The overall objective of the present project is to analyze the role of central monoaminergic mechanisms in the pathophysiology of schizophrenic psychosis and for the mechanism of action of antipsychotic drugs. Biochemical events in the cerebrospinal fluid, related to activity changes in the central monoaminergic neurons, will be analysed in schizophrenic patients and healthy volunteers before and in relation to drug treatment. Biochemical parameters of current interest represent the major monoamine metabolites HVA, MOPEG and 5-HIAA, as well as the pituitary hormone prolactin which we recently showed to be present in the human CSF. In a separate project, the central monoamines in patients will be labelled by inhalation of O18. The changes in specific activity of the labelled monoamine metabolites in the CSF and the urine will be analysed in schizophrenic and depressive patients before and during drug treatment.